A centrifuge can receive containers for samples and can be used for separating components of the samples contained therein at high rotational speed of a centrifuge rotor. In the case of a floor-stand centrifuge which is arranged on the floor and has a height which reaches up to a worktable, there is a fair amount of space for the components of the device. In the case of a desktop centrifuge however which is arranged on worktable, a low overall height is desired so that the available space within the centrifuge needs to be utilized well. This leads to the consequence that the upper side of a centrifuge rotor is disposed relatively close to the cover of the centrifuge. If this distance is smaller than the distance of the bottom side of the rotor to the floor of the bowl of the centrifuge, the upper side of the rotor will be pulled more strongly to the cover than the bottom side of the rotor is pulled towards the floor of the bowl. This can be explained by Bernoulli's principle. This usually leads to the consequence that an upwardly directed force generally acts on the centrifuge rotor. Lifting force in the amount of 100 N can be generated at a rotational speed of approximately 6,000 rpm in a conventional centrifuge. This is promoted even further in that the upper side of the rotor mostly has a large planar surface which rotates only a few millimeters beneath the cover of the centrifuge, whereas the bottom side of the rotor has a rugged geometry in which an attraction force according to Bernoulli is produced only to a lower extent.
The aerodynamic influence can further be supplemented by a dynamic influence, e.g. as a result of an external impulse of the centrifuge. In the case of such an impulse, it may occur that the elastically held motor will incline to the side and axial forces will be generated which superimpose on the lifting force of the rotor.
In order to enable the control over the aerodynamic and dynamic influences, rigid locks are used in centrifuges according to the state-of-the-art. They reliably prevent any axial displacement of the rotor at high rotational speeds. The locks require special tools in order to attach them and release them again in a secure fashion, so that the mounting work before and after a centrifuging run requires a relatively large amount of time. Moreover, there are locks which act depending on the speed, so that during standstill or at low speed the rotor can be withdrawn from the drive head against a low amount of force. Such a lock will only work reliably if the lifting forces are always smaller than the locking forces. Such a configuration is not suitable for all combinations of rotor and centrifuge and is also difficult to calculate as a result of the difficult determinability of the lifting forces by dynamic influences.
It is thus an object to provide a centrifuge which ensures reliable locking against axial lifting forces acting against the centrifuge rotor during standstill, low and high rotational speeds, with the locking force increasing even further in the axial direction with the rising rotational speed of the centrifuge rotor. Furthermore, the rotor should be able to be mounted on and dismounted from the drive head in a very short period of time and without any special tools.